Heating unit and method of making the same



y 1939- L. WIEGAND 2,158,600

HEATING UNIT AND METHOD OF MAKING THE SAME Filed Sept. '7, 1935 3 Sheets-Sheet l Edwin. Lwizsqxui.

IN JLNToQ B x 11m,

ATTORNLTSr y 1939- E. 1.. WIEGAND 0 HEATING UNIT AND METHOD OF MAKING THE $AME Filed Sept. 7, 1935 3 Sheets-Sheet 2 1N viva TOR AT TOR NL&

Edwin. Lwiosand May 16, 1939- E. L. WIEGAND HEATING UNIT AND METHOD OF MAKING THE SAME Filed Sept. '7, 1935 5 Sheets-Sheet 5 Edwin. L-W

iogandl lN LuToQ Y ATTo mu 2* 5 Patented May 16, 1939 UNITED STATES PATENT OFFICE THE 8 Edwin L. Wiegand, Pittsburgh, Pa.

Application September 7, 1935, Serial No. 39,576

14 Claims. I

My invention relates to electrical heating units and the method of making the same, and the principal object of my invention is to provide a new and improved electrical heating unit and method of making the same. In the drawings accompanying this specification, and forming a part of this application, I have shown, for purposes of illustration, one form of my electrical heating unit and the method of making it. In the drawings:

Figures 1 through 10 show details of the electrical heating element proper and steps in the method of making it,

Figures 11 through 17 show details of a heat radiating casing, for the heating element proper, and steps in the method of making the same,

Figures 18 and 19 illustrate a step in the method of assembling the heat radiating casing with the heating element proper,

Figure 20 is a perspective view of one end of a completed heating unit,

Figures 21 through 24 show details of the electric terminal end of the heating unit and steps in the method of making the same,

Figure 25 is a plan view of a completed heating unit, and

Figure 26 is a fragmentary section, taken along the line 26-26 of Figure 25, looking in the direction of the arrows.

In making the heating element proper, hereinafter termed the heating element, an elongated flat strip of suitable sheet metal is drawn into the form of a channel 30, as shown in perspective in Figure 1, the flanges 31, 32 of the channel being here shown of equal depth and as extending at right angles to the bottom 33 of the channel. The width of the flat strip sheet metal is preferably so chosen that when it is bent to the desired form to form a closed or substantially closed sheath, the upper edges of the flanges 31, 32 will come into nearly edgewise abutment, as will more fully hereinafter appear. The channel 30 is desirably so formed that rounded fillets 34., 33 form the junctionsbetween the flanges 31, 32 and the bottom 33 of the channel.

The channel 30 will serve to be substantially formed into a sheath surrounding an electrical resistor embedded in a suitable highly refractory compacted heat conducting electrically insulating material, and to this end suitable compactible refractory insulating material 36 in granular or finely subdivided form and of an impressionable character is sifted into the channel 30, as for example set forth in my Patent 1,398,410, of November 29, 1921. The material 33 is sifted into During this operation the insulating material 38 1 is compressed to a desired extent. The resistor 31 is indicated in Figures 3 and 4 as comprising a helically wound resistance wire disposed lengthwise back and forth within the channel 33, but it will be apparent to those skilled in the art that 15 the resistor 31 may assume other forms and be disposed in other ways in the channel.

The terminal ends 38, 33 of the resistor 31 are provided, in this instance, with fiat metallic connectors 40, 4| extending longitudinally of the 20 axis of the channel, and mechanically and electrically connected respectively to the terminal ends 38, 39 of the resistor 31 in any suitable way.

In order to confine the insulating material 36 at the otherwise open ends of the suitable means such as a block 42 may be provided disposed in the channel 30 at its right hand end, as viewed in Figures 1 and 4, and at the left hand end a two-part block 43, 44 may be disposed within the channel, this two-part block '30 comprising a lower part 44 disposed below the connectors 411, 41 and of such thickness as to locate the connectors at the desired distance from the bottom of the channel 30, and an upper part 43 sufliciently high to close off the remainder of the left hand end of the channel 30. Each of the parts 43, 44 of the composite block may be provided with registering recesses 45, 46 and 41, 43 within which the ends of the terminals are disposed and held. The composite block 43, 44 thus also serves to hold the connectors 40, 41 in position while the insulating material is being acted upon by dies. It will be noted that the block 42 occupies a certain desired length of the right hand end of the channel and keeps that length 45 free of insulating material fora purpose which will appear.

When the resistor 31 has been submerged as shown and described in connection with Figures 3 and 4, additional insulating material 43, pref- 5 erably the same as the material 36, is sifted into the open channel 30 to a desired depth, as diagrammatically indicated in Figure 6. A die 53, fitting within the open portion of the channel 30 is then brought down on theinsulating material 5 channel 30, 25

49 thereby tightly compacting the entire body of insulating material 36, 49 and causing it to dispose itself between and about the parts of the resistor, tightly against the surfaces of the resistor to eliminate air pockets. The die 5|] for giving this preliminary compacting to the insulating material preferably has tapered down== wardly extending knife-like projections 5t, 52 at its longitudinal margins, the inner surfaces 53, 54 of which form flllets corresponding to the fillets 34, 35 joining the flanges 3i, 32 and bot-- tom 33 of the channel 36, so that when the die 50 is removed from the channel 6d after having compressed the insulating material, the insu lating material will have longitudinally extend ing rounded edges 55, 56 adjacent the flanges of the channel. a

At this stage in the process the insulating material 36, 49, while hard, still contains moisture and the process of making the heating element may be continued without, at this stage, removing the moisture, but, preferably, the channel with the contained insulating material and resistor embedded therein are now dried in an air drying oven. Thereafter the upper ends 627, 56 of the flanges 3i, 32 are bent toward each other, as by a suitable die (not shown), around the upper longitudinal rounded edges, 55, 56, of the compacted insulating material, as indicated for example in Figure 8. If desired, the insulating ma terial may be dried at this stage of the process. The channel 30, now partially formed as a sheath, is then, while disposed in a matrix die 53, subjected to the compressing action of a die 60, analogous to the preliminary compressing die 56, as indicated in Figure 9. In Figure 9 the die 66 is shown as having completed its sheath-forming and compressing action and as having been withdrawn from contact with the now closed sheath 6|. The insulating material within the sheath 6| is now highly compressed and compacted.

The sheath 6| is now removed from the lower die, 59, in any suitable way, as by pressing upwardly on pins such as the pin 62. The end of the sheath 6|, opposite from the end from which the connectors 40, 4| extend, is now subjected to the action of a die (not shown) which crushes the end to the form shown in Figure 10, so that the end will be in the shape of a channel 63 comprising a composite bottom 33a formed by a portion of the bottom 33 of the original channel 30 and the end portions of the original flanges 3|, 32, and composite flanges formed by portions of the original flanges 3|, 32, folded together to form double wall flanges 64, 65. The adjacent margins 66, .61 of the crushed down end portions of the original flanges 3|, 32 may be fastened together, as by brazing or welding 68 or in any other suitable manner. If desired the insulating material may be dried at this stage of the process. In any event, the heating element is now baked at a red heat.

The heating element is to be provided with a heat conducting and radiating casing, and to this end a metallic sheath 69, preferably seamless, of suitable length, and of such internal crosssectional outline, as shown in perspective in Figure 11, as to fit slidably over the sheath 6| of the heating element, has an annular bead or flange 10 formed thereon, as by drawing out and folding together a portion of the sheath 69, as shown in perspective in Figure 12 and in longitudinal cross-section in Figure 13. This flange, 10, serves as an abutment for one end of a cup member (shown in perspective in Figure 14 and in longitudinal cross-section in Figure 15), of generally ovoid cross-section, having an aperture H2 in its bottom adapted to fit slidably onto the sheath 69. The cup member II, in this instance, is provided with a bracket 13 which may be brazed or welded or otherwise suitably fastened to the cup member H. The bracket 13 comprises a portion l4, desirably fitting and fastened to the surface of the cup member M and a plane offset portion l5 provided with an aperture it for a purpose which will appear.

After the cup member ll, with its attached bracket l3, is-slipped over the end of the sheath Gil into abutment with the flange ill, the end ll of the ssheath 66 is spun out over and against the bottom of the cup ll, as shown in Figure 15, thereby firmly holding the cup member M to the sheath 66.

The sheath 66 is then provided with radiating fins l8, ltd, tilt, and so on. Each fin 18, 18a, and so on is, in this instance, separately formed and each fin constitutes a transversely extending flange at one end of a separate ferrule 19, 19a, and so on, having an internal cross-sectional outline slidably fitting the sheath 69. The unflanged end of each ferrule M, Ma has a slightly inwardly tapered outside edge 66, whereas the flanged end of the ferrule H! has a slightly 0ut- I wardly tapered or flared entrance margin 8|, so

that as the flanged ferrules are successively slipped over the sheath 69, as indicated in Figure 1?, the outwardly flared entrance margins 8| are forced against the inwardly tapered edges 86, in tight engagement therewith. The relative proportions as between the length of the sheath 69 and the length and number of ferrules 19 is desirably such that the unfianged end 8| of the last ferrule placed upon the sheath 69 will assume a position approximately at the beginning 82 of the channeled end 63 of the heating element when the heating element is assembled with the heat radiating casing.

When the heat radiating casing, comprising the sheath 69, the flanged ferrules 19, 19a, and so on, and associated parts, has been completely assembled, as hereinbefore described, this casing is slipped over the heating element sheath 6|, from the channeled end 63 thereof toward the connector end, until the spun out part Tl firmly engages a flared out part 83 of the end of the sheath 6| of the heating element, as shown in Figure 18. The flared out end part 83 may be formed on the sheath 6| during the compressing operation preformed by the die 60 of Figure 9.

When the heat radiating casing and the heating element have been thus assembled they are placed between a pair of matrix dies, 84, 85, the inside operating surfaces of which when brought together, as shown in Figure 19, conform generally in cross-sectional outline to that of the ferrules I9, and are provided with transversely circumferentially extending slots 86 adapted to freely accommodate the fins 18, 18a, and so on. The assembled heating element sheath 6|, heat radiating sheath 69, and ferrules 19 are then highly compressed and formed to final shape, the insulating material within the sheath 6| being also further compressed. This brings the ferrules l9 and the sheath 69 and the sheath 6| in close heat conducting relation with each other and with the insulating material within the sheath 6|. It is of course obvious that in order to highly compress and form to final shape the heating element sheath 6|, the heat radiating sheath 69, the ferrules I9, and the insulating material within the sheath 5|, it is necessary that the area defined by the cross-sectional outline of the operating surfaces of the dies 84, 85, when the dies are brought-together as in Figure 19, be substantially less than the area defined by the cross-sectional outline of one of the ferrules I9. It will be further evident that the crosssectional area of the finished finned element is accordingly locally constricted at the sections where the dies 84, have thus acted on the element. Nothing further need be done to retain the finned ferrules on the sheath 69. The end of the sheath 69 may be crushed down, at the same time, to form a channel shaped end 81 snugly enveloping and in contact with the channel shaped end 63 of the heating element, This may be done, for example, by providing the upper die 84 with a suitably formed extension 88.

The composite channel shaped end formed by the combined channel shaped ends of the sheath 6| of the heating element and the casing sheath 59 may have its bottom 89 provided with an aperture (not shown) through which insulating bushlugs 90, 9| may be disposed, these bushings being fastened together and to the channeled end by means of a tubular rivet 92, as shown in Figure 20.

When the parts have been acted upon by the dies 84, 85, the cup member II is partially filled with a refractory insulating material 93, as in dicated diagrammatically in Figure 21, the material being preferably of such type that it will harden. readily. An insulating block 94, shown in perspective in Figure 22, is then inserted into the cup member Hand forced against the insulating material 93 contained therein. The insulating block 94 is of such transverse cross-Sectional outline as to fit slidably within the cup member II, and is provided with a pair of spaced longitudinally extending apertures 95, 96, generally oblong rectangular in cross-section, through which the connectors 40, 4| are adapted to loosely pass. Additional readily hardenable insulating material (not shown), such as the material 93, also may be introduced in the spaces 91 between the connectors 40, 4| and the inside walls of the apertures 95, 96, particularly if, as indicated in Figure 23, these spaces are not filled when the insulating block 94 is rammed against the insulating material 93 in the cup member II.

After the insulating block 94 has been disposed in the cup member 'II the free margin 98 of the cup member is spun around and onto a shoulder 99 on the insulating block, the shoulder 99, in this instance, being formed by and at the junction between a reduced end I00 of the block and a larger body portion I 0|.

A pair of terminals I02, I03 are then respectively fastened to the ends of the connectors 40, 4I, as, for example, by at least one rivet I04 for each terminal and connector and by additionally spot welding each terminal to each connector, as at the spots I05. The terminals I02, I03 are here shown as made of fiat metal stampings, each terminal having a longitudinally extending portion I06 offset from an end portion I01 which is fastened to the resistor connector, as above described. The longitudinally extending portions I06 are thus spaced somewhat further apart than the connectors 40, 4|, and if desired, may each be provided with an arcuate recess I08, the recesses being substantially concentric when the terminals I02, I03 are fastened to the connectors 40, 4|. Each terminal I02, I03 may be provided with apertures I09 for making electrical lead connections thereto.

The completed heating unit appears in plan as shown in Figure 25, and the electric terminal end of the unit may be mounted on any suitable support, here indicated as a plate IIO. To this end an insulating bushing III is provided, having a boss II2 disposed within the aperture H5, in the bracket 13, along with another insulating bushing II 3, disposed at the other side of the bracket 13, and having a recess I I4 in which the boss I I2 fits. Any suitable fastening may be provided, such as a screw-threaded bolt II5, extending through registering apertures H6 in the insulating bushings III, H3 and through an aperture II I in the plate H0, and being threaded through a nut II8 on the other side of the plate. It will of course be obvious that the bracket I3 may be held to and mounted on a support in other suitable ways.

The other end of the heating unit may be held to and mounted on a support by any suitable fastening means passing through the tubular rivet 92 in the insulating bushings 90, 9|. It will be understood that the insulating bushings 90, 9| may be formed analogously to the bushings III, II3, so that the tubular rivet 92 will be out of contact with the bottom 89 of the channel shaped end of the heating unit.

It will be evident that the connectors 40, 4| need not extend from the sheath 6| at the end thereof but may extend through any opening provided therethrough.

From the foregoing it will be apparent to those skilled in the art that the illustrated'embodiment of my invention provides a new and improved electrical heating unit, readily and conveniently constructed and assembled by and resulting from a new and improved method, and accordingly, accomplishes at least the principal object of my invention. On the other hand, it also will be obvious to those skilled in the art that the illustrated embodiment of my invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of my invention, or sacrificing all of the advantages thereof, and that accordingly, the disclosure herein is illustrative only, and my invention is not limited thereto.

I claim:

1. The method of making an electrical heating unit, including: telescoping metallic sheath means over a. sheathed electrical heating element having a resistor connector extending therefrom; disposing insulating means around said connector and within a portion of said sheath means and against said heating element; and then bending a portion of said sheath means over the margin of said insulating means to hold said sheath means and said heating element assembled.

2. An electrical heating unit, comprising: a metallic sheath having an opening; a resistor within said sheath; a connector, connected to said resistor and disposed through said opening; a separate member; laterally extending flanges on said sheath; said separate member having a portion disposed between and held by said flanges; and means, including said separate member, constructed and arranged to support said connector.

3. An electrical heating unit, comprising: a number of telescoped metallic sheath means having openings; said sheath means being so constructed and arranged that a generally annular space is left between portions of two of said teleit'll n impressionable state in an open scoped sheath means, said space having a local constriction; a resistor within said sheath means; a connector, connected to said resistor and disposed through at least one of said openings; and means, including insulating material disposed in said space at least in part on opposite sides of said construction, constructed and arranged to insulate said connector from said sheath means.

l. An electrical heating unit, comprising: a,

number of telescoped metallic sheath means having axially spaced openings; a resistor within said sheath means; a connector, connected. to said resistor and disposed through at least one of said openings; means, including insulating material, constructed and arranged to insulate said connector from said sheath means; said insulating material being in engagement with the margin of an opening of an inner one or" said sheath means; and an outer one of said sheath means having a rein oi its opening disposed inwardly over a margin of said insulating material.

The method oi making an electrical h ating element, which includes: embedding resistor it compactihle relractory insulating material in im ressionable state in an open sheet metal .iei, applying force to compact said material out said resistor within said channel y] le leav- .id channel in its open state, thereby to bring s insulating material to a predetermined crosssection 1 shape, and then applying force to bend the flanges of said channel toward each other and ag st the exposed surface of said insulating naterial form a substantially con lnuous heath around said material, leaving said insu ating material with substantially said predeerrnined cross-sectional shape.

6. ng element, which includes, embedding a resistor in. compactih-le refractory insulating material channel, applying force to compact said material about said resistor within said channel while leaving said channel in its open state, thereby to ioring said insulating material to a predetermined c3 -sectional shape, said force being so applied in so compacting said insulating material the upper surface thereof is formed so that it has convex longitudinal margins adjacent the Walls or said open channel, and then applying force to hand the flanges of said channel toward each other and against and around said convex longitudinal margins respectively, leaving said insulating material with substantially said predetermined cross-sectional shape.

7. The method of making an electrical heating element, which includes, embedding a resistor compactiioie refractory insulating material in an impressionable state in an open sheet metal channel, and applying force to compact said material about said resistor within said channel while leaving said channel in its open state, thereby to bring said insulating material to a predetermined cross-sectional shape, said force being so applied that in so compacting said insulating material the upper surface thereof is so formed that it has convex longitudinal margins adjacent the walls of said open channel, and then applying force to bend the flanges of said channel toward each other and against and around said convex longitudinal margins respectively, and against said upper surface of said insulating material to form a substantially continuous sheath around said material, leaving said insulating material with substantially said predetermined cross-sectional shape.

The method of making an electrical heat sheet metal aitacoo 8. The method of making an electrical heating unit, provided with heat radiating means, ineluding: inserting an electrical heating element, having a metallic sheath provided with a laterally outwardly extending projection at one end, into a metallic heat radiating sheath until said projection engages an end of said heat radiating sheath, and subjecting the other end of said heat radiating sheath to pressure to bring opposite inside wall portions thereof into proximity.

9. l he method of making an electrical heating unit, provided with heat radiating means, m eluding: inserting an electrical heating elem 5 having a metallic sheath provided with a la ally outwardly extending projection at one e and a channel shaped portion at the oth into a metallic heat radiating sheath u projection. engages end of heat sheath, suhjecting said heat radiatin pressure to compress said h at against said heating element sheath, a ing the other end of 5 heat into channel shape comp-lendentary said cha el shaped portion of sh 10. An QEBiZl'lo metallic sheath t'lith i said insulating s port said an electrical heatin unit, conr ii i metallic sheath having an opening; t thin. said sheath; means, within sheath, for insulating said resistor from said sheath; a connector, connected to said resistor and disposed through said opening; and means, includ ing a separate metallic member carried L" d sheath, coaxialiy with said opening, lating material disposed within said separate member for insulating said connector from said separate member, constructed and arranged to support said connector.

12. An electrical heating unit, comprising: a. metallic sheath having an opening; a resistor within said sheatl means, within said sheath, for insulating said resistor from said sheath; a connector, connected to said resistor and disposed through said opening; and means, including a separate metallic member insulated from said connector and carried by said sheath and surrounding said connector at said opening and co-extending with said connector away from said opening, constructed and arranged to support said connector.

13. An electrical heating unit, comprising: sheath means including a number of telescoped metallic sheath means, an outer one of said telescoped sheath means having an end opening spaced axially beyond the corresponding end opening of an inner one of said telescoped sheath means; a resistor within said inner sheath means; means, within said inner sheath means, for insulating said resistor from said inner sheath means; a connector, connected to said resistor and disposed through said openings; and means, including insulating material disposed within said outer one of said telescoped sheath means and disposed at least in part axial- 1y between said end openings. constructed and arranged to support and insulate said connector from said sheath means.

14. The method of making an electrical heat 5 ing unit, provided with heat radiating means,

including: inserting an electrical heating element, having-a metallic sheath provided with a channel shaped portion at an end thereof, into an end of a metallic heat radiating sheath until 10 said channel shaped portion substantially registers with the other end of said heat radiating sheath, subjecting said heat radiating sheath to pressure to compress said heat radiating sheath against said heating element sheath, and forming said other end of said heat radiating sheath 5 into channel shape complementary to and around said channel shaped portion 01' said heating element sheath.

EDWIN L. WIEGAND. 

